medium5.0
CVE-2026-34983
Wasmtime has use-after-free bug after cloning `wasmtime::Linker`
Impact
Wasmtime is a runtime for WebAssembly. In 43.0.0, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. Specifically, the following steps must occur to trigger the bug clone a wasmtime::Linker, drop the original linker instance, use the new, cloned linker instance, resulting in a use-after-free. This vulnerability is fixed in 43.0.1.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| rust | wasmtime | = 43.0.0 | 43.0.1 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Bytecodealliance | Wasmtime | Version 43.0.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-hfr4-7c6c-48w2
- https://github.com/advisories/GHSA-hfr4-7c6c-48w2
- https://nvd.nist.gov/vuln/detail/CVE-2026-34983
- https://rustsec.org/advisories/RUSTSEC-2026-0090.html
- https://github.com/pypa/advisory-database/tree/main/vulns/wasmtime/PYSEC-2026-151.yaml